Energy storage devices that simultaneously have or provide high energy and power densities with superior cycle life and low cost are desired or sought for use in many and various actual and potential applications including vehicle electrification, consumer electronics and other industrial products. For example, in the past two decades, Li-ion batteries (LIBs) have revolutionized portable electronic devices, and have the potential to make a great impact on vehicle electrification. Unfortunately, state-of-the-art rechargeable batteries like Li-ion batteries are typically characterized by having a low power density. Because of their low power densities, the time required to recharge a Li-ion battery can be very long, a significant problem currently having no satisfactory available solutions. Thus, in spite of their immense potential, state-of-the-art LIBs have not been able to fully satisfy or meet the needs and demands of vehicle electrification wherein there is a need and a demand for both energy and power densities higher than those offered by current technology.
Supercapacitors (SCs), also known as electrochemical capacitors or ultracapacitors, are another type of energy storage devices. While SCs typically have much higher power densities than LIBs, SCs generally have substantially lower energy densities than LIBs. Currently, there is no SC product having desirably high power density and high energy density available in the market.
In the past two decades, substantial research and investigative efforts have been directed towards improving the energy densities of both LIBs and SCs. For LIBs these efforts have included synthesis of new high-capacity, high-voltage electrode materials, nanostructure design of anodes and cathodes, and development of high voltage electrolytes. Novel battery architectures have also been investigated. In the SC arena, the efforts have included utilization of graphene to increase surface area, introduction of pseudocapacitance, use of ionic liquid electrolytes, and development of asymmetric SCs. These studies have resulted in significant advancements in energy densities of LIBs and SCs. However, to date achieving or attaining LIBs with a specific energy >240 Wh/kg and SCs with a specific energy >100 Wh/kg remains a significant challenge. Furthermore, in state-of-the-art SCs, the thickness of the electrodes is typically limited to less than 100 μm because of slow ion diffusivity.
Recently, there have been some reports of the development of what have been referred to as three dimensional LIBs. In present practice, however, these three dimensional LIBs have generally been limited to what can be perhaps more appropriately referred to as “thin films.” That is, these so-called three dimensional LIBs can have large dimensions in the x-y plane, but the size in the z-direction is limited to micrometers or less. Consequently, proposed applications for this class of cells has typically been limited to uses as surface-mountable rechargeable batteries such as for applications in microelectromechanical systems (MEMS) and other small electronic devices, and termed as 3D-microbatteries.
In view of the above, there is a need and a demand for electrode architecture design such as can be applied to either or both LIBs and SCs to increase their energy densities while providing high power densities.